<html>
    <head>
        <title>Test</title>
        <style>


stack { display:block; flow:stack; size:*; }
stack > frame { size:*; visibility:none; }

stack > frame:expanded { size:*; visibility:visible; }


        </style>
        <script type="text/tiscript">

event click $(button|radio) {
  if(var c = $(stack > frame:expanded)) c.state.collapsed = true;
  $(stack)[this.index].state.expanded = true;
}


        </script>
    </head>
    <body>
      <div><button|radio>First plugin</button>
           <button|radio>Second plugin</button></div>
      <stack>
        <frame src="plugin1.htm" />
        <frame src="plugin2.htm" />
      </stack>
    </body>
</html>